1. Field of the Invention
This invention relates to dental equipment, specifically, a reusable handpiece handle assembly interconnected with a disposable drill head assembly.
2. Description of the Related Art
Conventional high speed dental handpieces are one piece assemblies having an integrally coupled hand portion and head assembly. A rotary turbine is located in the head assembly. The turbine is driven at high speeds of approximately 150,000 to 300,000 rpm by compressed air applied to the turbine. The rotary action of the turbine turns a burr attached to the axle of the turbine. The burr is used for dental drilling. Air and water are delivered to the head assembly of the handpiece through tubing in the handle connected to a conventional dental stand which provides compressed air and water to the handpiece.
Conventional high speed dental handpieces are difficult to clean. In the process of drilling, organic matter and bacterial residue enter the head assembly of the handpiece and become attached to the intricate interior parts of the handpiece. The build up of foreign matter on the interior parts of the head assembly of the handpiece presents two problems: first, the organic matter and bacterial residue, and any diseases therein, may be transmitted to other dental patients by the force of the compressed air applied to the turbine; second, the build-up of foreign matter on the intricate parts of the handpiece eventually reduces the speed at which the handpiece operates to an extent that the handpiece becomes non-functional and must be replaced. Cleaning the intricate interior parts of the handpiece is not possible through normal disinfecting and sanitizing procedures such as rinsing or flushing. Autoclaving has been used to clean dental handpieces, however, autoclaving has proven :extremely time consuming and causes severe deterioration of the handpiece, thereby lessening the usable life-span of the device.
Dental handpieces with disposable drill heads have been introduced to address the cleaning problems inherent in conventional dental handpieces. Balson (U.S. Pat. No. 3,955,284) discloses a disposable dental drill assembly which has a drill head assembly that may be disposed after each use of the handpiece while the handle of the handpiece may be retained.
However, due to the arrangement of the turbine in the drill head assembly of the Balson device, the device has difficulty maintaining adequate drill speeds when pressure is applied to the burr of the device. The turbine, or rotor member, rotates about stub shafts that extend axially from the turbine blades. The stub shafts are located in seats in the drill head housing. When pressure is applied to the burr the pressure is transmitted directly to the stub shafts, forcing the shafts frictionally against the seats, thereby significantly reducing the speed of the burr.
Furthermore, Balson does not disclose means to accurately introduce air or water at the drilling area. Conventional dental handpieces have air and water passages that terminate adjacent the burr so that air and water may be accurately directed to the actual working surface of the dental drill. Balson does not provide air and water passages in the disposable drill head assembly. A water passage is provided in the neck of the device, a distance away from the actual working surface of the drill. The distance between the actual working surface of the drill and the water passage reduces the accuracy of delivery of water to the working surface.
Balson also does not provide protection against foreign matter entering the handle. A passage extends from a compressed air source through the handle of the device into the disposable drill head assembly. Compressed air is delivered to the turbine through the passage. Foreign matter that has accumulated in the drill head assembly may be sucked back into the passage in the handle upon cessation of application of compressed air to the turbine. The foreign matter may subsequently be transmitted to other dental patients by reapplication of compressed air through the passage even though a new drill head has been attached to the device.